Simplified low insertion force sealing device capable of self restraint and joint deflection

ABSTRACT

A conduit coupling system for use with a spigot includes a bell and a sealing device. The bell is adapted to mate with the spigot. The bell includes a first end and a second end. The bell has a concave annular inner surface and a diameter of the annular inner surface adjacent to the first end of the bell is greater than a diameter of the annular inner surface adjacent to the second end of the bell. The sealing device includes a locking segment including a convex outer surface and a K-type gasket coupled to a locking segment or a non-restraining anti-extrusion segment. The sealing device is adapted to fit between the bell and the spigot.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application Ser. No. 61/250,160, filed Oct. 9, 2009, entitled “Parabolic Ramp Self-Restraining Bell Joint,” and U.S. provisional application Ser. No. 61/301,462, filed Feb. 4, 2010, entitled “Simplified Low Insertion Force Sealing Device Capable of Self Restraint and Articulation,” both of which are hereby specifically and entirely incorporated by reference.

BACKGROUND

1. Field of the Invention

The invention is directed to couplings and methods of coupling, particularly to bell and spigot couplings and methods. The couplings can be between pipes, fittings, and/or other piping components. The couplings allow for greater pipe deflection and stronger joint retention, with less force needed on insertion.

2. Background of the Invention

Members of the flow control industry, such as producers of pipeline components for the transmission of water, gas, oil, or other fluids have focused substantial attention on the problem of creating and maintaining connections between adjacent lengths of pipe, or pipes and fittings, or pipes and valves. In applications where the fluid, such as water for fire mains or water distribution in municipalities, is under high pressure, various means are used to prevent separation of the joints between piping components. Piping components are joined to prevent separation caused by thrust forces, earth movement, and external mechanical forces exerted on piping components. These components include, for example, pipes, couplings, fittings, valves, and fire hydrants. The majority of the solutions can be categorized into either “push-on joints,” “mechanical joints,” or “flanged joints.”

Iron pipe has traditionally been used to withstand the large pressures that are necessary for municipal water systems and other systems. Those pressures are needed to carry fluids over long distances, to carry large amounts of fluids, and to prevent contamination of the systems in the event of a hole or other breach of the system. There are two related problems in the history of using pipes of any sort, including iron pipes—(1) creating a secure seal to join the pipes and to withstand large pressure, and (2) bending or deflecting the joints of the pipes to meet the intended use of the pipes.

The first substantial use of cast iron pipe was in Europe in the 17^(th) century. The piping systems of the 17^(th) and 18^(th) centuries primarily had flanged ends that bolted together with lead or rawhide gasket's for scaling. Flanged joints continue to be used for some applications today, but with rubber gaskets. Flanged joint systems are costly to install and require considerable maintenance.

The first bell and spigot joint was developed by Thomas Simpson of the Chelsea Water Company in England in 1785. The joint was caulked with jute rope impregnated with pine resin or tallow and sealed in place with molten lead. The bell and spigot joint remained the predominant pipe joint until the advent of the push-on joint, for example the TYTON® Joint, in 1956.

There are numerous methods of securing piping components in series to make up a pipeline, roughly divisible into three main categories: (1) rigid, as with bolted flange connections; (2) flexible, as with numerous designs such as TYTON® push-on joints and gaskets, or TYTON® combined with self-restraining gaskets bearing toothed inserts, such as FIELD LOK 350® Gaskets, providing both sealing and autonomous restraint; and (3) others with a limited amount of incidental flexibility, such as PVC Pipe with Rieber Gaskets where minor flexibility is possible due to the plasticity of the gasket and pipe materials and to joint tolerancing.

Push-on solutions are exemplified by U.S. Pat. No. 2,953,398, and account for the majority of straight-run pipe connections. In a typical configuration, a spigot of a pipe slides into a bell of another pipe past a tightly fitted gasket. A variation of the push-on joint is evidenced by U.S. Pat. No. 2,201,372, which employs a compression snap-ring fitted within a special lip of the bell, in order to exert pressure onto locking segments and thus drive them into the spigot, restraining the joint against thrust forces. U.S. Pat. No. 3,445,120, likewise employs a gasket with toothed, locking segments encased therein that are generally disposed such that they and the gasket may roll between a locked and a free position. As the gasket bulb rotates under extraction forces, it is intended to eventually to encounter a position in which the segments must compress the gasket to allow further rotation of the segment and engagement of the teeth with the mating pipe spigot, thus, terminating the rotation and compression of the gasket bulb and restraining the joint.

Other examples of restrained push-on joints include those disclosed in U.S. Pat. Nos. 5,295,697, 5,464228, and 5,067,751. In those references; the connection is effected by either locking segments or wedges within the gasket that engage the spigot. The locking segments possess a groove that mates with an annular rib on the bell, such that the rib acts as a rocker, or cam, or during some movements, as a wedge. During insertion of the spigot into the bell, the segments rotate on the rib, but are prevented from appreciable axial movement by the mating of the rib and groove. Upon experiencing counter-forces tending to effect removal of the spigot, the rib acts as a cam, both causing the segments to pivot on the rib as an axis, and exerting a radially inward pressure as the segment attempts to slide past the rib. These types of joints depend on compressive force on the rubber gasket to maintain the connection of the pipes.

While the push-on type joint has obtained wide acceptance for pipe joints, acceptance for fittings, valves, and hydrants is much lower. The contours of bell sockets of the push-on joint require a high degree of precision for a cast surface. In restrained joints, an additional locking joint is necessary, which also requires a high degree of precision to manufacture. It often takes a high degree of skill and alignment precision, as well as substantial force (i.e. in the range of 600 to 800 pounds of force for an eight, inch size pipe), to assemble joints using the above described push-on type joints. The insertion force with present push-on designs increases proportionally with conduit diameter. Moreover, insertion forces increase substantially in low-temperature conditions.

A current trend in the industry is to manufacture pipe with walls much thinner than the current designs. Whether the pipe end is produced in a manufacturing plant or is the result of field cuts required to adjust the length of the pipe, such pipes cannot realistically be beveled or have rounded ends. Damage to the gaskets or displacement of the gaskets is a likely outcome when inserting a spigot end of a pipe not properly aligned or without a beveled or rounded end into the bell of another push-on joint pipeline component. A further consequence of the high assembly forces required is that installers favor mechanical joint connections for fittings, valves, and hydrant shoes because they require lower assembly forces.

Attempts to design low insertion resistance-joints have been made in the past but these designs were not completely satisfactory because normal conical inner surfaces do not allow for sufficient deflection ° Nile bell and socket joint. For example, U.S. Pat. No. 3,815,940 and U.S. Patent Application Publication No. 2009/0060635 both show bells with conical inner surfaces. Cast iron pipe is rigid and does not permit deflection. Creating ductile iron pipe permits slightly greater deflection at the joint. However, that deflection carries an increased risk of loss of pressure. If the joint is a straight connection, no deflection is possible. If the joint is connected into a cone-shaped annulus, deflection of more than a few degrees would degrade the connection opposite the angle of deflection, ultimately leading to a greater potential for a loss of pressure. Small movements in the earth could, over time, cause leaks in underground piping systems.

Thus there is a need for a connection that is less sensitive to misalignment and temperature extremes, has reduced frictional resistance to the insertion of the spigot until the desired connection is achieved and the coupling is maintained, yet maintains a seal under high pressures, even when the joint is deflected.

SUMMARY OF THE INVENTION

The present invention overcomes the problems and disadvantages associated with current strategies and designs and provides new devices and methods for connecting bell and spigot pipeline components. Specifically, one embodiment of the invention solves the problem created by cone-shaped joints by using a parabolic-shaped joint. The joint is less likely to lose restraint and pressure as the joint is deflected, permitting deflections up to 10 degrees, preferably between 9 and 5 degrees of deflection, and more preferably of 7 degrees of deflection or less. A 90-degree turn can thus be made using approximately 15 (20-foot) pipes over a distance of approximately 300 circular feet with deflections of 6 degrees, as opposed to 30 pipes over a distance of 600 circular feet using 3 degree deflection joints. That greater deflection reduces the number of bend fittings and the amount of trench digging required, and conserves land space.

An embodiment of the invention is directed to a conduit that comprises at least one bell with an end face, an internal portion, and a concave inner surface between the end face and the internal portion. The diameter of the inner surface adjacent to the internal portion is greater than the diameter of the inner surface adjacent to the end face.

In preferred embodiments, the inner surface is a truncated elliptic paraboloid. In preferred embodiments, the conduit has a bell at a first end and a spigot at a second end. Preferably, the conduit is cylindrical and is made of at least one of ferrous metals (e.g. steel and cast iron), non-ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE).

Another embodiment of the invention is also directed to a conduit that comprises multiple openings and at least one opening has a bell that couples to another piping component having a spigot. In preferred embodiments, the inner surface of the bell of the invention is concave. The inner surface is preferably a truncated elliptic paraboloid. In preferred embodiments, the conduit has a bell at a first end and a spigot at a second end. Preferably, the conduit is cylindrical and is made of at least one of ferrous metals (e.g. steel and cast-iron), non-ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE).

Another embodiment of the invention is directed a sealing device. The sealing device comprises at least one segment having a convex outer surface, and a K-type gasket coupled to the segment. In the preferred embodiments, the segment is a locking segment. The locking segment functions as a restraining device and an anti-extrusion device to prevent the joint from separating and the elastomeric seal from being extruded out of the joint when subjected to high internal hydraulic forces. In other embodiments, a guide segment without teeth is substituted for the locking segment and serves as an anti-extrusion device for the polymeric material of the sealing portion.

In preferred embodiments, the segment is of a first material and the K-type gasket is of a second material. In preferred embodiments the K-type gasket is comprised of a coupling section and a sealing section. The sealing section is preferably comprised of an upper section and a lower section, each extending from the coupling section. The coupling section, in preferred embodiments, has one or more expansion or contraction grooves in the outer or inner periphery. The locking segment, in preferred embodiments, has at least one engagement device. Preferably, the engagement device is annular.

Another embodiment of the invention is directed to a conduit coupling system. The system comprises at least two piping components and a sealing device. A first component has a bell and a second component has a spigot, the spigot is adapted to mate with the bell. The bell includes a first end and a second end, wherein the first end coupled to the first component. The bell socket has a concave annular inner surface and a diameter of the annular inner surface adjacent to the first end of the bell socket is greater than a diameter of the annular inner surface adjacent to the second end of the bell socket. The sealing device with a segment comprising a convex outer surface and a K-type gasket coupled to the segment. The sealing device is adapted to fit between the hell socket and the spigot end.

In preferred embodiments, the segment is a locking segment. Each locking segment is adapted to engage an outer surface of the spigot. The inner surface of the bell socket is preferably a truncated elliptic paraboloid. Each component preferably comprises a bell at a first end and a spigot or bell at a second end and each component is cylindrical. Each component can be made of ferrous metals (e.g. steel and cast iron), non-ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE).

In preferred embodiments, the locking segment is of a first material and the K-type gasket is of a second material. Preferably, the first material is harder than the material of the spigot. In preferred embodiments, the K-type gasket has a coupling section and a sealing section. The sealing sections is preferably comprised of an upper section and a lower section, each extending from the coupling section. Preferably the locking segment has at least one engagement device. In preferred embodiments, the sealing device is annular.

Another embodiment of the invention is a method of coupling at least two conduits of the invention. The method includes the steps of positioning a sealing device inside a bell coupled to one end of a first conduit, inserting a spigot of a second conduit through the sealing device inside the bell, and partially removing the spigot from the bell. A locking segment of the sealing device engages the outer surface of the spigot as the spigot is partially removed from the bell. The sealing device is adapted to move axially within the bell in the direction of the insertion of the spigot and the movement is assisted by the presence of expansion and contraction grooves in the coupling section of the gasket. This movement allows the locking segment to be displaced from the path of the incoming spigot with little increase in insertion force. The axial movement May be confined to one segment of the sealing device to accommodate angular and radial misalignment of the incoming spigot. The scaling device is adapted to move in the direction of the partially removed spigot from the bell in response to internal hydraulic pressure to effect a seal to the spigot that rests in an angular and radial misaligned position.

In preferred embodiments, the bell has a first end and a second end, the first end is coupled to the first conduit. The bell has a concave annular inner surface, and a diameter of the annular inner surface adjacent to the first end of the bell socket is greater than a diameter of the annular inner surface adjacent to the second end of the bell socket.

In certain embodiments, radial loading of the locking segment increases as the spigot is removed from the bell. The radial loading of the locking segment can increase exponentially as the segment moves toward the front of the bell following the parabolic curve toward the vertex. Preferably, the includes at least one locking segment comprising a convex outer surface, and a K-type gasket coupled to the locking segment. Preferably the K-type gasket is compressed upon insertion of the spigot. The withdrawal of the spigot end can be due to external forces or internal hydraulic forces.

Other embodiments and advantages of the invention are set forth in part in the description, which follows, and in part, may be obvious from this description, or may be learned from the practice of the invention.

DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail by way of example only and with reference to the attached drawings, in which:

FIG. 1 is a partial cross-sectional view of an embodiment of the system of the invention.

FIG. 2 is a partial cross-sectional view of an embodiment of the bell of the invention;

FIG. 3 is a partial cross-sectional view of an embodiment of the gasket of the invention.

FIG. 4 a is a partial cross-sectional view of an embodiment of the locking segment of the invention.

FIG. 4 b is a partial cross-sectional view of an embodiment of the locking segment of the invention as it interacts with the inner surface of the bell socket.

FIG. 5 is a partial cross-sectional view of an embodiment of the anti-extrusion segment of the invention.

FIG. 6 is a partial cross-sectional view of an embodiment of the system with the spigot prior to insertion into the bell.

FIG. 7 is a partial cross-sectional view of an embodiment of the system with the spigot inserted into the bell.

FIG. 8 is a partial cross-sectional view of an embodiment of the system with the gasket compressed more on the upper side due to deflection of the spigot.

FIG. 9 is a partial cross-sectional view of an embodiment of the system with the locking segment engaged.

FIG. 10 is a cross-sectional view of an embodiment of the system with the spigot deflected within the bell.

FIGS. 11-13 are pictures of experimental engagement patterns.

DESCRIPTION OF THE INVENTION

As embodied and broadly described herein, the disclosures herein provide detailed embodiments of the invention. However, the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, there is no intent that specific structural and functional details should be limiting, but rather the intention is that they provide a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.

A problem in the art capable of being solved by the embodiments of the present invention is coupling piping components and maintaining the assembly. It has surprisingly been discovered that certain configurations of the interior surface of a bell socket increase ease of assembly and allow for deflection between components. Furthermore, it has surprisingly been discovered that certain configurations of the outer surface of a gasket increase the gasket's ability to maintain assembly during use of the components including under high pressure applications.

FIG. 1 depicts a cut away view of the components of the upper segment of system 100. System 100 includes a spigot 105, a bell 110, and a sealing device 115. Each of spigot 105, bell 110, and sealing device 115 is shown in partial cross-section. In the preferred embodiment, each of spigot 105, bell 110, and sealing device 115 is annular in shape having a common axis below FIG. 1. Each of spigot 105, bell 110, and sealing device 115 can have any diameter that may be commonly found in piping systems. Preferably the diameter of each of spigot 105, bell 110, and sealing device 115 is between one-half inch and one hundred and twenty inches, more preferably between one-half inch and seventy two inches.

In a preferred embodiment, system 100 is used to join lengths of pipes. The pipes can be of any length. Additionally, one pipe can have one spigot end and one bell end, two spigot ends, two bell ends, or a combination thereof. In other embodiments, there can be at least one spigot and/or bell located along the length of the pipe positioned perpendicularly or at an angle to the axis of the pipe. In other embodiments, system 100 can be used to join two or more pipes to other components (e.g. fire hydrants, valves, and/or fittings), or can be used to join components together. System 100 can be used for any fluid, for example gas, water, or oil. In the preferred embodiment, sealing device 115 has a gasket end 120 and a locking segment 125. However, in certain embodiments, segment 125 can be an anti-extrusion element (described herein).

In the preferred embodiment; piping components 105 are made of ductile iron, steel, or plastic and segments 125 are made of a substantially rigid material such as ductile iron, steel, or hardened plastic however other material may be used, preferably but not limited to ferrous metals (e.g. steep and cast iron), non-ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE). Pipes can have walls of any thickness, preferably, but not limited to, between ⅛ inch and 1¼ inches. Fittings can have walls of any thickness, preferably, but not limited to between ¼ inch and 2 inches.

In the preferred embodiment; sealing device 115 is of a diameter larger than spigot 105 and has an annulus at the back, with a diameter slightly smaller than the diameter of spigot 105. The sealing device 115 is preferably dimensioned such that spigot 105 can be inserted into sealing device 115 without encountering intentional resistance until such time as it reaches the inner end of bell 110. Insertion forces are reduced by several orders of magnitude compared to compression type seals. If resistance is encountered during insertion of the spigot into the locking segment, due to the plasticity of the gasket and assisted by the compression groove 330, the segment is able to reduce the resistance by moving up and away from contact with the spigot.

FIG. 2 depicts a cut away, view of a section of a bell 110. The center line of the bell 110 is illustrated by a dashed line 12. The outer shape of bell 110 is best described by the relative external diameters of the pipe's different points. Bell 110 has an external diameter at the point 205 and a smaller external diameter at point 206 some length along the bell 110. The transition of the external surface of bell 110 from point 205 to point 206 is a gradual curve providing that section of the bell 110 with the appearance of a bell. Preferably a constant external diameter is maintained between point 205 and 207 with a gradual change of external diameter from point 207 to 206. The internal section of the bell 110 (from point 205 to point 260) is referred to as the bell socket 220. Bell 110 is usually integrally formed but for the purpose of this disclosure can be divided into a number of sections.

The first section extends from point 205 to point 230. The internal radius of bell 110 between center line 12 and point 205 (R1) is greater than the internal radius of bell 110 between center line 12 and point 234 (R2). The transition of the inner surface from internal radius R1 to R2 is a smooth curve and is referred to as bell throat 225. An example of a smooth curve is a segment of a circle of predetermined radius. An effective radius 232 for the smooth transition depends on the distance from point 205 to point 230, internal radius R1 and internal radius R2. Preferably, radius 232 is adapted to facilitate insertion of spigot 105 into bell 110.

The second section of bell 110 extends from point 230 to point 231. The second section includes a retainer portion 233 extending from point 230 to point 234. The internal radius at point 230 is R2 and immediately transitions to an internal radius R3 between center line 12 and point 234. R3 is greater than R2. The portion of the second section from reference point 234 to reference point 231 is provided with an inner surface 235 that is concave with reference to the center line 12. The concave inner surface 235 may have a variety of shapes, including but not limited to a truncated cone, a truncated elliptic paraboloid, a truncated sphere, or a combination thereof. Preferably, the curve of an inner surface 235′ of a bell socket 220′ (shown in FIG. 4 b) has a nose or “vertex” of a paraboloid aligned in an axial direction opening away from the “directrix.” As explained herein, concave inner surface 235 and concave inner surface 235′ provide a function that enables the ease of assembly and allows for increased angle of deflection by spigot 105 inserted into the bell 110.

The third section of bell 110 extends from point 231 to point 240. The portion of the third section from point 231 to point 239 defines the heel seat for the gasket 120 and the portion of the third section of bell 110 from point 239 to point 240 defines the socket shoulder where the gasket 120 is held in place.

The fourth sections of bell 110 extends from point 240 to point 260. This section has a sloped portion 250 that is referred to as the clearance slope. The radius from the center line 12 to point 242 (R4) is larger than the external radius of the spigot 105 in FIG. 1. The second portion of the fourth section includes a relatively flat surface in the lower portion from point 242 to point 249 that is referred to as the land. The third portion of the fourth section extends from point 249 to point 260. Point 260 is referred to as the land stop and has an internal radius R5 that is substantially equal to the internal radius of spigot 105. Typically, spigot 105 is the end of the pipe opposite to pipe bell 110.

Illustrated in FIG. 3 is a cut away view of the upper segment of a gasket 120 used with the pipe bell 110 illustrated in FIG. 1. Gasket 120 is preferably made of an elastomer. However, other materials that are flexible, appropriate for the fluid, and provide alight seal can be used. For example, gasket 120 can be made of SBR (Styrene butadiene rubber), EPDM (ethylene propylene diene monomer rubber), Nitirile, NBR (Nitrile butadiene rubber), and/or other synthetic and natural rubbers. In the preferred embodiment, gasket 120 is of a single durometer rubber. However, in other embodiments, two or more durometer rubbers can be used. Gasket 120 is preferably a K-type, lip, or wiper seal design, conforming to and fitting within the bell 110. Gasket heel 305 and gasket shoulder 310 mate with gasket heel seat defined by the portion of the third section from point 231 to point 239 of bell 110 and socket shoulder 240 (as described with respect to FIG. 1). In the preferred embodiment, gasket heel 305 is slightly larger than the gasket heel seat, thereby compressing gasket heel 305 so that it is firmly anchored in bell socket 220 with gasket shoulder 310 against socket shoulder 240.

Gasket 120 has a front edge portion 315 (also referred to as the front edge slope or segment edge) adapted to be disposed facing towards the open end of bell 110 that is illustrated in FIG. 1. Gasket 120 also has a substantially cylindrical portion 320 that, when inserted into bell 110, forms a gasket orifice. Gasket 120 includes a primary translation slope 325. The primary translation slope 325 allows for compression and translation of the rest of the gasket 120 whenever force is exerted on the front portion 315. Gasket 120 has an expansion and contraction groove 330 formed on the upper surface. In the preferred embodiment, expansion and contraction groove 330 is an annular cutout along the outer surface of gasket 120. However, in other embodiments, expansion and contraction groove 330 can be located on the inner surface of gasket 120. In other embodiments, there can be multiple expansion and contraction grooves located at various locations about gasket 120. Furthermore, expansion and contraction groove 330 can have any cross-sectional shape, including but not limited to triangular, rectangular trapezoidal, and semicircular. The back edge of gasket 120 is formed as a concave pressure annulus pocket 340. Hydraulic pressure against pressure annulus pocket 340 increases the sealing pressure of lip seal 335 against the mating spigot 105. While annulus pocket 340 is shown as a single curved indentation, annulus pocket 340 can have multiple indentations and can have other shapes. Additionally, annulus pocket 340 can be of another material more compressible than the material of gasket 120.

The gasket heel seat, defined by the portion of the third section from point 231 to point 239, and socket shoulder 240 mate with and retains sealing device 115. In a preferred embodiment, adjacent to socket shoulder 240 is clearance slope 250. Clearance slope 250 permits passage of the water or other fluid into the pressure annulus groove of sealing device 115 (described herein). In a preferred embodiment, the inner portion of bell socket 220 is land 249, which extends from clearance slope 250 to land stop 260. Land 249 provides clearance for spigot 105 and limits over-deflection of the joint. Land stop 260 limits the insertion depth of spigot 105, while land radius 265 assists in casting by eliminating a sharp inner corner between land 249 and land stop 260.

Front edge slope 315 is the surface to which the locking segment 125 a or anti-extrusion segment 125 b is coupled. In the event that the edge of spigot 105 contacts the segment 125, in the preferred embodiment, front edge slope 315 is angled such that segment 125 and gasket 120 will be deflected outward and away from spigot 105, allowing the passage of spigot 105 through gasket orifice 320. Contraction groove 330 facilitates the bending or buckling of the gasket 120 and the gasket orifice 320. In operation, the primary translation slope assists in stabilizing the front portion of gasket 120 and transferring forces to the expansion and contraction groove 330, which will bend and/or buckle to assist in the movement out of the path of an inserted spigot 105 until spigot 105 comes into contact with the front edge of lip seal 335. The effect of moving a portion of the gasket 120 out of the path of an inserted spigot 105 is to substantially reduce the friction thereby reducing the amount of force necessary to insert the spigot 105 into the bell 110.

FIG. 4 a depicts a cut away view of the upper segment of segment 125, where segment 125 a is a locking segment. Locking segment 125 a is preferably made of AISI type 4140 steel (chromium steel). However other hard and durable materials can be used, for example AISI type 431 stainless steel. In preferred embodiments, segment 125 may be coated with an anticorrosion coating. The outer surface 405 of locking segment 125 a is preferably a curved surface that makes contact with the concave inner surface 235 of bell socket 220. The curvature of outer surface 405, as shown in FIG. 4 a, is merely for illustration purposes. The curvature can be greater or smaller than shown in FIG. 4 a. In the preferred embodiment outer surface 405 is convex, more preferably a truncated paraboloid. However; in other embodiments, outer surface 405 can be another convex surface, a linear surface, or a concave surface. Preferably outer surface 405 opens away from bell throat 225. When the outer surface 405 of locking segment 125 a moves against the inner surface 235 of bell socket 220, the locking element 125 acts as a cam follower and the inner surface 235 of the bell socket 220 acts as a cam. That cam action facilitates locking segment 125 a in wedging between bell socket 220 and spigot 105, forcing the teeth 410 of locking segment 125 a into the outer surface of spigot 105 and providing restraint against extraction of spigot 105. Due to the elasticity of gasket 115 locking segments 125 a have freedom to move to maintain contact between outer surface 405 and the inner surface 235 of bell socket 220. Thus, segment 405 can accommodate misalignments between the two surfaces caused by, for example, casting variability in the bell 110, as well as a differential caused by the elliptical path of the segments 125 a during deflection not matching exactly to inner surface 235.

The interaction between the outer surface 405 of locking element 125 and the inner surface 235′ of the bell socket 220′ is better illustrated in FIG. 4 b. As stated previously, inner surface 235′ of the bell socket 220′ is concave and in a preferred embodiment follows the shape of a truncated paraboloid. Therefore, for every horizontal displacement X of locking element 125 the action of the outer surface 405 of the locking element 125 against the inner surface 235′ the bell socket 220′ there will be a vertical displacement Y of the locking element 125 commensurate with the function defining the shape of inner surface 235′ of the bell socket 220′. While locking segment 125 a is shown with two teeth 410, one or more teeth can be used. For thin walled spigots or PVC spigots, there will be more teeth 410 located closer together than in embodiments using thick wall iron spigots.

Another function of locking segments 125 a is to assist in moving gasket 120 away from spigot 105 as spigot 105 is inserted into bell 110. Segment mounting slope 415 is angled such that the corresponding mating front end slope 315 of gasket 120 will help deflect gasket 120 up and away from the path of spigot 105 so that passage is not impeded. Locking segment 125 a is aided by primary translation slope 325 of gasket 120, which supports the portion of gasket 120 forward of expansion and contraction groove 330.

In the preferred embodiment, segments 125 are equally spaced and mounted to front end slope 315 of gasket 120. Segments 125 reinforce the elastic gasket material against extrusion between throat 225 and spigot 105. In order for segment teeth 410 to penetrate spigot 105, it is preferable for locking segment 125 a to be made of a material harder than spigot 105.

FIG. 5 depicts a cut away view of the upper segment of segment 125, where segment 125 b is an anti-extrusion segment for non-restraining joint gaskets. In embodiments where restraint between a mating bell 110 and spigot 105 is not desired or needed, segment 125 b can be made without teeth as shown in FIG. 5. The toothless segment 125 b functions similarly to the locking segment 125 a in helping gasket 120 to facilitate deflection and preventing, extrusion of gasket 120 between throat 225 of bell socket 220 and spigot 120, but has no teeth to penetrate spigot 105 and provide restraint. In some embodiments, both locking segments 125 a and toothless segments 125 b can be used in the same restraining device 115.

FIGS. 6-9 depict cut away views of the steps of inserting socket 105 through sealing device 115 and into bell 110. In FIG. 6, spigot 105 is aligned with bell 110. In the preferred embodiment, the centerline of spigot 105 is aligned with the center line of bell 110. However, in other embodiments, spigot 105 can be inserted into bell 110 at an angle. The angle can be less than 15°, preferably, the angle is between 5° and 9°, and more preferably the angle is 7° or less. Upon contact and continued insertion of spigot 105 (as shown in FIG. 7), lip seal 335 will bend and stretch over spigot 105 imparting axial and circumferential tensile forces to gasket 120. The tensile forces cause the secondary translation slope 345 to force segments 125 into contact with spigot 105.

Insertion of spigot 105 through sealing device 115 will result in spigot 105 contacting locking segment 125. Ordinarily this would increase the friction exerted in spigot 105. However, in the preferred embodiment, as spigot 105 contacts locking segment 125, the forces exerted on the gasket 120 cause the gasket 120 to bend at contraction groove 330 and allow for the longitudinal and axial displacement of segment 125 along concave inner surface 235. The displacement of the gasket allow and guide the translation of segment 125 out of the way of incoming spigot 105 with a minimum force.

The displacement of segment 125 is caused by a combination of axial and radial movement in response to the orientation of the incoming spigot 105 and dimensional variations of the joint components. The displacement of segment 125 can include off-axis rotation of segment 125 in response to spigot 105 being deflected or offset. The energy stored in gasket 120 as a result of the displacement keeps segment 125 in contact with spigot 105. Insertion of spigot 105 through sealing device 115 induces axial tensile forces in sealing device 115, or at least positions segment 125 to better engage spigot 105 when there is a withdrawal of spigot 105 from bell 110 (as shown in FIG. 8). The circumferential tensile forces exerted on lip seal 335 to form a seal between lip seal 335 and spigot 105. The seal is amplified when the joint is pressurized and the material of gasket 120 causes the seal to be pressed more tightly against spigot 105 and the inner surface of bell 110 (as shown in FIG. 8). Gasket 120 can move independently of segment 125 once segment 125 is seated. Spigot 105 does not have to be fully inserted into bell 110 to seal. In the preferred embodiment, spigot 105 will be sealed once the inserted end of spigot 105 is inserted past lip seal 335, at which point, system 100 is water tight.

Once the spigot 105 is in place, the spigot 105 or the bell 110 may be subjected to separation forces that tend to separate the spigot 105 from the bell 110. The separation forces may arise either from external forces or as a result of the internal pressure in the pipe. As shown in FIG. 9, separation forces cause the teeth 410 to engage spigot 105. The teeth 410 are engaged, due to radial loading caused by the outside surface of the segments 125 bearing against the progressively decreasing curved inner surface 235 of bell 110. Since, in the preferred embodiment, bell 110 is shaped such that the diameter decreases at an increasing rate from the gasket heel seat, defined by the portion of the third section from point 231 to point 239, to bell throat 225, withdrawal of the spigot is met with increasing resistance as the similarly formed outer surface 405 of segments 125 is wedged between the bell 110 and the mating spigot 105. The flexibility that allows segment 125 to translate out of the path of the incoming spigot 105 also allows segment 125 to rotate into an off-axis position to maximize the engagement of teeth 410 with a misaligned or radially offset spigot 110 and to reduce the possibility of point-loading conditions.

When the joint is extended (pulled apart), the outer surface 405 of segment 125 mates with the inner surface 235 of bell socket 220 and forces teeth 410 into the outer surface of spigot 105 due to the parabolic wedging action of the outer surface of locking segment 125 being drawn in the direction of its vertex. Withdrawal of spigot 105, either due to external forces or the internal hydraulic action caused by pressurizing the joint, causes teeth 410 to engage spigot 105 and the convex outer surface 405 of locking segment 125 to engage the corresponding concave inner surface 235 of bell socket 220. As the withdrawal motion is continued, the engagement between the outer surface 405 of locking segment 125 and inner surface 235 is intensified by the increasingly smaller diameter of bell socket 220. This increases the inward radial loading on teeth 410, forcing them to further engage spigot 105. Extension of the joint is minimized due to the outer surface of locking segment 125 encountering an exponentially decreasing diameter of the inner surface 235 during pull-back, which exponentially increases the rate of radial loading of teeth 410 engaging spigot 105. In embodiments where there are multiple locking segments, the engagement pressure on the outer surface of locking segments 125 would be relatively equal since bell 110 and spigot 105 are in the form of concentric circles when axially aligned.

FIG. 10 depicts a cross-sectional view of a spigot 1005 coupled to a bell 1010 deflected at an angle θ and away from full engagement FE in the bell socket 220. The outer surface of segment I 025 facilitates a deflection, or bending, of the joint between spigot 1005 and bell 1010 by moving along inner surface 1020 of bell 1010. If θ is defined as the angle of deflection as measured from the centerline CL of the bell 1010 and spigot 1005 components, then in the direction of deflection, segment 1025 will move along curve 1020 in the direction of the vertex, or smaller end of curve 1020. At the-other end of the coupling, in the opposite direction away from deflection, the opposing segment 1035 will move along the curve 1020 away from the vertex. Segments mounted around the gasket 1015 at intermediate locations between segment 1025 and segment 1030 will follow an elliptical path. The outer surfaces of these intermediate segments will maintain contact with the concave inner surface 1020 of bell 1010 due to the continuously changing shape of inner surface 1020. The major axis of the elliptical path can be defined by h=tangent (θ) times the effective diameter as measured across the outside surface of opposing segments. In the preferred embodiment, θ is less than or equal to 15°, more preferably θ is less than or equal to 10°, however, θ can be another angle.

In the preferred embodiment, when the joint is deflected, the outer surface of locking segment 125 follows a curve described by an ellipse in a plane inclined to the axis of the spigot. Each half of the ellipse on either side of the minor axis is a curve close enough in shape to a parabola so that the ellipse conforms closely to the paraboloid of bell 110 as the joint is deflected.

In the preferred embodiment, the inner surface 235 of bell 110 and the outer surface 405 of segment 125 follow the shape of truncated paraboloids, one positioned inside the other. The two paraboloids are axially aligned when the joint is in the undeflected position. Paraboloids are surfaces generated by rotating a parabola about its central axis.

In the preferred embodiment, no lubrication between spigot 105 and scaling device 115 is required. However, in other embodiments, lubricants can be used, for example dry film lubricants. The lubricant can ease in assembly and provide corrosion protection to sealing device 115.

In 8 inch pipe, for example, the force used to insert the spigot 105 into the bell 110, is between 25 to 100 pounds. With that level of force the insertion can be completed manually, without the use of mechanical devices other than to lift the piping component.

The following examples illustrate embodiments of the invention, but should not be viewed as limiting the scope of the invention.

Example

An experiment using two lengths of 8 inch pipe was conducted. One pipe had a bell as described herein while the other had a spigot as described herein. The two lengths were joined using a sealing device as described herein. The pipes were sealed at their respective open ends and the internal cavity was pressurized. The experiment was conducted first with the pipes having no deflection and then with the pipes having 5.7° and 7.0° of deflection. The results are compiled in Table 1.

TABLE 1 No. of Joint Minimum Maximum Test Seg- Deflec- Pressure, Pressure, Number ments tion, ° psi psi Test Result 1 8 0 700 772 Leak: Gasket Tear 2 8 0 700 771 Leak: Gasket Tear 3 14 0 700 1192 Leak: Gasket Tear 4 10 0 700 998.5 Leak: Gasket Tear 5 10 5.7 700 828.2 Leak: Gasket Tear  6* 14 0 700 1067.3 No failure  7* 14 7.0 700 1028.6 Leak from prior damage to gasket *Same gasket was used for Tests 6 and 7. Gasket sustained damage in removal after Test 6.

If “θ” is defined as the angle of deflection between the axis of the bell socket and the spigot, through moderate angles of deflection, the locking segments following the major axis of an ellipse projected onto a plane inclined at θ° perpendicular to the axis will, on the side of the complementary angle (180°−θ) be positioned nearer the vertex of the paraboloid of the bell socket, and those on the corresponding angle of deflection, θ, corresponding to the longer side of the major axis of the ellipse will follow the curve of the paraboloid and be positioned further out on the major axis, but still in close proximity to the bell socket. Thus the elliptical path of the deflected segments rotating within the paraboloid helps maintain proximity between the paraboloid outside surfaces of the locking segments and the paraboloid surface of the bell socket through moderate angles of deflection within the limits of the joint. At the center of rotation (during deflection), the segments are not displaced much beyond that of their original position on the circle perpendicular to the axis of the spigot. The displacement or translation of the segments includes the ability to rotate into an off-axis position to improve the engagement with a misaligned spigot and to provide equalization of pressure between the bell curve and the spigot end through the segments. Thus, the engagement pattern of the segments is approximately balanced around the spigot whether deflected or not through moderate angles of deflection of the joint. The advantage of this embodiment is that the joint less likely to lose engagement or restraint as the joint is deflected, permitting deflection angles up to 10 degrees, preferably between 5 and 9 degrees, and more preferably 7 degrees or less. A 90-degree turn can thus be made using approximately 15 (20-foot) pipes over a distance of approximately 300 circular feet with deflections of 6 degrees, as opposed to 30 pipes over a distance of 600 circular feet using 3 degree deflection joints. That greater deflection reduces the number of bend fittings and the amount of trench digging required, and conserves land space.

The validity of this assertion can be seen by the engagement pattern of segment teeth of a gasket on a pipe spigot as shown in FIGS. 11-13 for a joint that was deflected 5.7°, and pressurized to 828.2-psi before the gasket body ruptured. It can be seen that the engagement pattern follows an elliptical path about the pipe spigot, and the depth of penetration of the teeth are approximately equal, indicating relatively equal pressures between the bell socket, segments and spigot, even though the joint is deflected. The joint in the photographs withstood a pressure of 828.2-psi before failure of the prototype gasket made of a catalyst-activated polyurethane. Even thought the gasket rubber failed, the joint maintained engagement and did not separate. The joints did not separate in any of the tests; all failures were due to leaks caused by tearing of the rubber when the tensile strength was exceeded due to internal pressure.

Other embodiments and uses of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. All references cited herein, including all publications, U.S. and foreign patents and patent applications, are specifically and entirely incorporated by reference. It is intended that the specification and examples be considered exemplary only with the true scope and spirit of the invention indicated by the following claims. Furthermore, the term “comprising” includes the terms “consisting of” and “consisting essentially of,” and the terms comprising, including, and containing are not intended to be limiting. 

The invention claimed is:
 1. A conduit for arrangement as a joint with a spigot, the conduit comprising: at least one bell, wherein the at least one bell includes: a curved convex bell throat that extends from an end of the conduit to a plane orthogonal to a longitudinal axis of the conduit; a concave inner surface adjacent to the bell throat; a retainer portion that extends orthogonally, with respect to the longitudinal axis of the conduit, from the curved convex bell throat to the concave inner surface, wherein the retainer portion intersects both the curved convex bell throat and the concave inner surface; a cylindrically-shaped heel seat adjacent to the concave inner surface, the heel seat extending from the concave inner surface in an axial direction parallel to the longitudinal axis of the conduit; a socket shoulder intersecting the heel set and extending from the heel seat in a radial direction orthogonal to the longitudinal axis of the conduit; a clearance slope extending axially and radially inward from the socket shoulder; a land, the land intersecting the clearance slope axially inward from the socket shoulder, the land extending in the axial direction, the land disposed axially inwardly from the concave inner surface; and a land stop, the land stop disposed axially inwardly from the land at a diameter smaller than a diameter of the land; and a sealing device including a segment and a gasket having a heel, a lip seal, and an inner gasket surface, the lip seal and the heel spaced axially inward from the segment, the inner gasket surface facing radially inward and extending between the segment and the lip seal, the heel contacting the heel seat, the lip seal extending radially inward from the inner gasket surface; wherein the diameter of a first point of the concave inner surface adjacent to the bell throat is smaller than the diameter of a second point of the concave inner surface distal from the bell throat, wherein the heel seat is axially inward from the second point of the concave inner surface, wherein the concave inner surface is a truncated paraboloid surface, wherein the truncated paraboloid is proximate the bell throat, and wherein a diameter of the bell at the bell throat is smaller than a diameter of the land such that the conduit is arrangeable with an angle of deflection with respect to the spigot when arranged as the joint.
 2. The conduit of claim 1, wherein the conduit comprises a bell at a first end and a spigot at a second end.
 3. The conduit of claim 1, wherein the conduit is cylindrical.
 4. The conduit of claim 1, wherein the conduit is made of at least one of ferrous metals, non-ferrous metals, and plastic.
 5. The conduit of claim 1, wherein the heel seat is adapted to receive a segment having a surface area that is disposed in contact with the truncated paraboloid.
 6. The conduit coupling system of claim 1, wherein the angle of deflection is between five and nine degrees. 